While Boris is being a bit apocalyptic in his comments I'm not sure we can accuse him of lying.
He's quoted as saying: "Heathrow is already by far the noisiest airport in Europe, about a hundred times worse than Paris."
While the first part of his statement can't be disputed, I can't think of any metric that supports the 100x assertion.
In round terms, there are about 5x as many people living within Heathrow's 55db Lden contour than within CDG's (roughly three quarters of a million vs about 150,000)